[Show abstract][Hide abstract] ABSTRACT: We discuss eight major challenges in the field of carbon nanomaterial toxicity. Generally, we pick up some of them, and the most important challenge is searching of the qualitative relationships between nanofactors and cytotoxicity. This is important since it can provide the possibility of conscious changes of carbon nanotubes cytotoxicity by manipulation with selected nanofactors. Therefore, the toxicity of a series of gradually oxidized carbon nanotubes is studied. We show, for the first time, that toxicity of those materials depends strongly on the ratio of acidic to basic group concentration—the higher is this ratio value, the more toxic are nanotubes. In this way, by changing this ratio, one can change toxicity. This correlation is more evident after ultrasonication, and it is connected with the accessibility of charged groups for interactions with proteins. Toxicity also depends on the ability of nanotubes for protein adsorption. We suggest that the changes in the protein composition of medium, especially lack of important growth factors, inhibit cell proliferation.
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[Show abstract][Hide abstract] ABSTRACT: GCMC technique is used for simulation of CO2/CH4, CO2/N2 and CH4/N2 mixtures adsorption (at 298 K) on six porous carbon models. Next we formulate a new condition of the IAS concept application, showing that our simulated data obey this condition. Calculated deviations between IAS predictions and simulation results increase with the rise in pressure as in the real experiment. For weakly adsorbed mixture component the deviation from IAS predictions is higher, especially when its content in the gas mixture is low, and this is in agreement with the experimental data. Calculated activity coefficients have similar plots to deviations between IAS and simulations, moreover obtained from simulated data activity coefficients are similar qualitatively as well as quantitatively to experimental data. Since the physical interpretation of activity coefficients is completely lacking we show for the first time, that they can be described by the formulas derived from the expression for Gex for the ternary mixture. Finally we also for the first time show the linear relationship between the chemical potentials of nonideal and ideal solutions and the reduced temperature of interacting mixture components, and it is proved that the deviation from ideality is larger if adsorption occurs in more microporous system.
Full-text · Article · Feb 2015 · Physical Chemistry Chemical Physics
[Show abstract][Hide abstract] ABSTRACT: A series of hydrosilated stationary phases were compared with respect to their hydrophilic–hydrophobic properties. The stationary phases were also compared to the bare silica gel used for this synthesis. The investigations were done using microcalorimetric measurements of methanol and acetonitrile heats of immersion. Because these stationary phases are used in both the reversed-phase and aqueous normal phase modes of liquid chromatography, the excess isotherm of water from acetonitrile solution was measured.From the materials tested the highest polarity was exhibited by the silica hydride and the bare silica. The Diamond Hydride is less polar. The highest hydrophobicity is exhibited by the hydrosilated stationary phase which contains bonded octadecyl ligands.
No preview · Article · Feb 2014 · Journal of Colloid and Interface Science
[Show abstract][Hide abstract] ABSTRACT: This paper presents the numerical analysis of spherical carbon adsorbents produced by the single-step steam pyrolysis of a polystyrene-divinylbenzene resin. The porous structure of the materials produced this way was easily controlled by varying such factors as the carbonization temperature, atmosphere or the heating rate, allowing carbonaceous materials to have a controlled microporous structure. Due to their unique properties, the obtained adsorbents can be considered applicable in various processes in technology and environmental protection. The fast multivariant fitting procedure with the new adsorption numerical models of the LBET class was used for the analysis of the microporous structure. The computer calculations using the LBET class models with the fast multivariant identification procedure were carried out with the application of the nitrogen (77.15 K) adsorption isotherms.
Full-text · Article · Oct 2012 · Applied Surface Science
[Show abstract][Hide abstract] ABSTRACT: We studied the thermodynamics of benzene adsorption on a series of oxidized closed-ended multiwalled carbon nanotubes at 298 K. Combined experimental and simulation results showed the significant effect of the surface heterogeneity on the benzene adsorption enthalpy and entropy at low surface coverages. For oxidized carbon nanotubes and low benzene uptakes, the differential entropy of the adsorbed phase is close to the differential entropy of solid benzene. Therefore, benzene molecules interacting with surface heterogeneities are ordered in quasi-solid structures at 298 K. At higher surface coverages, the ordering and packing of benzene molecules is liquid-like.
No preview · Article · Jun 2012 · Chemical Physics Letters
[Show abstract][Hide abstract] ABSTRACT: The calorimetric measurements of methanol and hexane heats of immersion were carried out on different silica gels. Based on the difference in immersion heats, a methodology for the determination of the number of silanols on the surface is presented. The calculated concentration of residual silanols on the silica gel surface agreed with data found in the literature. The proposed methodology, based on a calculation of possible hydrogen bond formation, was also tested on the series of bonded stationary phases with different coverage densities. A very good correlation between the calculated number of accessible residual silanols and the coverage density of bonded ligands was observed.
Full-text · Article · Sep 2011 · Journal of Chromatography A
[Show abstract][Hide abstract] ABSTRACT: A detailed description of the stationary-bonded phase surface in reversed-phase liquid chromatography (RPLC) is a topic of great interest in separation sciences. For this purpose, the thermal effects connected with solvent adsorption on the series of octadecyl stationary-bonded phases were investigated. Microcalorimetric study of organic solvent heat of immersion of the stationary-phase and chromatographic measurements of the silanol activity were executed. Good correlation between the heat of immersion of different solvents and the residual silanol activity obtained from chromatographic tests of various stationary phases are observed. The present data suggest that measurement of solvent adsorption heat governed by polar interaction with residual silanols may be a useful tool for the determination of silanol activity and surface topography. The present methodology allows determining the access of the solvent molecules to the residual silanols on the chemically bonded phase surface based on silica gel.
[Show abstract][Hide abstract] ABSTRACT: A simple method of preparation of new high surface area spherical carbon adsorbents is presented. The phosphoric acid activation upon hydrothermally formed spherules was employed to produce carbons having controlled high specific surface area (over 2100m(2)/g), large volumes of pores (1.2cm(3)/g), and high acidity. Prepared from sucrose materials show high adsorption capacities (i.e. 220mg/g(C)) toward paracetamol. It is proved that for these materials the contents of surface phosphorus are responsible for the reversibility of drug adsorption/release process.
Preview · Article · Feb 2011 · Journal of Colloid and Interface Science
[Show abstract][Hide abstract] ABSTRACT: A detailed, molecular-level description of the sorption mechanism in reversed-phase liquid chromatography is of great interest to analytical chemists. For this purpose, solvent adsorption in the octadecyl stationary bonded phase was investigated. Preferential adsorption of solvents from an acetonitrile-water and methanol-water mobile phase was measured on a series of non-end-capped octadecyl bonded phases with different coverage densities of bonded ligands using the minor disturbance method. For a comparison, a microcalorimetric study of organic solvent adsorption on the stationary phase was executed. The results from the excess isotherm measurement agree well with the experimental measurement of the heat of immersion of the bonded stationary phases by the test solvents. The microcalorimetric measurement is another method for determination of solvation processes of the stationary phases. Changes of the heat of immersion provide information about the surface accessibility for interaction with solvent molecules. The increase of the stationary phase coverage density reduces the free space between bonded chains and penetration of solvent between organic chains.
Full-text · Article · Sep 2010 · Journal of Colloid and Interface Science
[Show abstract][Hide abstract] ABSTRACT: Using the combined techniques of molecular simulation, simple analytical modeling, and adsorption calorimetry, we propose new models describing adsorption onto closed carbon nanotubes. The models are capable of describing the adsorption isotherms and calorimetric enthalpy of carbon tetrachloride adsorption measured on three different closed carbon nanotubes. It is shown that the assumption of the presence of two types of surface centers (high- and low-energy centers) on external tube surfaces is sufficient to describe experimental adsorption and calorimetric enthalpy data.
Full-text · Article · Sep 2010 · Journal of Colloid and Interface Science
[Show abstract][Hide abstract] ABSTRACT: a b s t r a c t The enthalpy of immersion of closed-end carbon nanotubes in a series of organic liquids has been mea-sured. The enthalpy was found to be linear function of the dipole moments. From the slope of the lines the average electrostatic field strength of the surface was calculated. This value increases with the decrease in tube radius. The curved aromatic fragments of C 24 H 12 have been employed as models of car-bon nanotubes (n, 0), where n varies from 30 up to 180. Theoretical results indicate that the reactivity indices also depend strongly on the surface curvature being linearly correlated with the surface electro-static field strength.
Preview · Article · Jan 2010 · Chemical Physics Letters
[Show abstract][Hide abstract] ABSTRACT: Using the single-set steam pyrolysis of Dowex 50 WX-2 (a polystyrene-divinylbenzene resin), Spherical Carbon Adsorbents (SCAs) were prepared. The porous structure of the materials obtained was easily controlled by varying the heating rate, allowing carbons having a controlled ratio of micropores to mesopores to be obtained. These materials are promising for the adsorption of phenol from aqueous solutions. Moreover, due to the relatively small amount of irreversibility exhibited in such adsorption, they could find potential use in environmental protection.
[Show abstract][Hide abstract] ABSTRACT: A series of commercial unmodified and modified activated carbons was studied. The surface chemical composition was characterized using X-ray photoelectron spectroscopy and Boehm titration methods. Data on p-nitrophenol (pnp) adsorption isotherms determined under real oxic and anoxic conditions (at 310 K) are presented and described using bimodal Langmuir and lattice density functional theory models. The applicability of the pnp molecule for determination of surface area using adsorption from solution data is discussed. It is shown that under anoxic conditions adsorption and relative enthalpy of this process depend on the value of BET apparent surface area and DA micropore volumes. The differences between adsorption levels under both conditions increase with rise in solute equilibrium concentration. Moreover, the average difference between adsorption values under both conditions increases and next decreases with rise in the concentration of surface acidic groups. Applying quantum chemical calculations, we show that under anoxic conditions the influence of surface oxygen groups on pnp adsorption is small, whereas under oxic conditions the reverse situation is observed. Obtained theoretical results show very good correspondence to the experimental data and the origin of the relationships observed experimentally is explained and discussed.
Full-text · Article · May 2008 · Journal of Colloid and Interface Science
[Show abstract][Hide abstract] ABSTRACT: The purpose of the current study is to present the state of art in the field of analytical description of water sorption on carbons. We discuss the most important and promising models proposed recently (for example by Mahle; Talu and Meunier; and Malakhov and Volkov) as well as some older theoretical models inspired by the pioneering ideas proposed in the papers of Dubinin, Serpinsky, Barton, D'Arcy, Watt, Do and Do and others. The applicability, advantages, and defects of all these analytical formulas are pointed out and some new approaches in this field are presented. The special attention is paid to the finite adsorption space and the possible involvement of partial chemisorption, i.e. the existence of various types of the hydrophilic centres. Since the calculation of isosteric enthalpy from an adsorption equation, and the comparison of theoretical enthalpy plot with the values measured calorimetrically, is the fundamental condition for the verification of the correctness of an adsorption model, for all considered models we show the corresponding adsorption enthalpy equations. The validity of all mentioned above models is verified for the data measured for five water-activated carbon systems. Finally, a summary of obtained results and some perspectives and suggestions for the description of experimental data are presented. From the analysis of experimental data it is seen that developed recently- the heterogeneous Do and Do model is probably the most successful for the simultaneous description of water adsorption and enthalpy of adsorption results.
Full-text · Article · Apr 2008 · Advances in Colloid and Interface Science
[Show abstract][Hide abstract] ABSTRACT: W celu otrzymania sferycznych węgli aktywnych (SWA) o dobrze rozwiniętej
powierzchni przeprowadzono badania procesu karbonizacji komercyjnej żywicy jonowymiennej
(Dowex 50 WX2). Nowatorska (dla tego prekursora węglowego) metoda
karbonizacji/aktywacji w strumieniu pary wodnej w temperaturze 900°C pozwoliła
uzyskać karbonizat o powierzchni BET bliskiej 1600 m2/g przy zachowaniu
kulistego kształtu granul. W pracy analizowano czas zgazowania, który wpływa
w zasadniczy sposób na objętość mezo- i mikroporów. Otrzymane materiały charakteryzują
się znaczną pojemnością sorpcyjną podczas adsorpcji fenolu.
[Show abstract][Hide abstract] ABSTRACT: The goal of this chapter is to show results of systematic
calculations for adsorption from binary non-electrolyte
solutions using Lattice Density Functional Theory
(LDFT). It is shown that several of the basic types of
adsorption isotherms in the experimental classification proposed by Giles et al. can be predicted from LDFT with reasonable estimates for the
adsorbent-adsorbate and adsorbate-adsorbate interaction energies. Varying the values of
the energetic parameters allows one to investigate the behaviour of adsorption isotherms
for solutions, the phase transitions that can occur, and the changes from one
classification to another. LDFT predictions are compared with experimental results
published by several authors. Moreover we show the fitting of LDFT model to
experimental data of sorption on activated carbons.
[Show abstract][Hide abstract] ABSTRACT: Badano adsorpcję SO2 na serii azotowanych węgli D43/1. Otrzymane dane opisano,
stosując model CMMS Malakhova i Volkova. Stwierdzono, że uzyskane z opisu
danych wielkości stałych modelu CMMS korelują z zawartością tlenu wyznaczoną na
podstawie analizy elementarnej. Otrzymane wyniki prowadzą do wniosku, że jeśli
proces sorpcji SO2 prowadzony jest bez dostępu tlenu i wilgoci, za wzrost zdolności
adsorpcyjnych węgli w stosunku do SO2 nie jest odpowiedzialny powierzchniowy
azot, lecz powierzchniowy tlen grup funkcyjnych. Zatem w takich warunkach nie
obserwuje się mechanizmu utleniającej adsorpcji SO2.
[Show abstract][Hide abstract] ABSTRACT: Podstawowym celem tej pracy było określenie wpływu chemicznej natury powierzchni
na adsorpcje N2, Ar i C6H6 z fazy gazowej. Podjęto się tego typu badań, gdyż
w literaturze brak jest systematycznej analizy danych adsorpcji najpopularniejszych adsorbatów
na chemicznie modyfikowanych adsorbentach węglowych. Badania przeprowadzono
na dwóch grupach materiałów węglowych. Pierwszą grupę stanowiły cztery
węgle aktywne otrzymane z odpopielonego oraz chemicznie modyfikowanego węgla aktywnego
D43/1. Węgiel ten był modyfikowany za pomocą HNO3, oleum i gazowego amoniaku.
Doprowadziło to do zmiany właściwości węgla D43/1 od amfoterycznych do kwasowych
i zasadowych. Druga grupa adsorbentów (układy odniesienia) składała się
z dwóch węgli aktywnych: ściśle mikroporowatego węgla D55/2 oraz węgla PICA HP, posiadającego
znaczącą ilość szerszych mikroporów oraz wąskich mezoporów (w całkowitej
porowatości) w porównaniu z pozostałymi adsorbentami. Z analizy izoterm adsorpcji
N2, Ar i C6H6 widać, że zastosowana metodyka modyfikacji chemicznej natury nie doprowadziła
do drastycznych zmian porowatości badanych węgli D43/1. Podsumowując,
w naszej opinii powyżej wymienione adsorbaty mogą być z powodzeniem stosowane do
charakteryzacji porowatości chemicznie modyfikowanych adsorbentów węglowych.